The invention generally relates to an improved catalytic process for decomposing alkyl or aromatic hydroperoxides to form a mixture containing the corresponding alcohol and ketone. In particular, the invention relates to decomposing a hydroperoxide by contacting it with a catalytic amount of a heterogeneous Au catalyst that has been treated with an organosilicon reagent.
Industrial processes for the production of mixtures of cyclohexanol and cyclohexanone from cyclohexane are currently of considerable commercial significance and are well described in the patent literature. In accordance with typical industrial practice, cyclohexane is oxidized to form a reaction mixture containing cyclohexyl hydroperoxide (CHHP). The resulting CHHP is either decomposed or hydrogenated, optionally in the presence of a catalyst, to form a reaction mixture containing cyclohexanol and cyclohexanone. In the industry, such a mixture is known as a K/A (ketone/alcohol) mixture, and can be readily oxidized to produce adipic acid or caprolactam, which are important reactants in processes for preparing certain condensation polymers, notably polyamides. A high K/A ratio in the reaction mixture is generally preferred. Due to the large volumes of adipic acid consumed in these and other processes, improvements in processes for producing adipic acid and its precursors can be used to provide beneficial cost advantages.
Druliner et al., (WO 98/34894) used a heterogeneous gold catalyst in an improved catalytic process for decomposing alkyl or aromatic hydroperoxides to form a mixture containing the corresponding alcohol and ketone.
Two common problems in CHHP processes, especially in heterogeneous catalytic processes, are the presence of water and acidic byproducts in the CHHP containing reaction mixture. Both of these can deactivate the catalysts, resulting in lower conversion rates and/or lower K/A ratios. One method to eliminate the acidic byproducts is by the addition of a neutralization agent, such as that described in U.S. Pat. No. 4,238,415. This, however, results in undesirable salts, which need to be removed from the final product. In situ drying of the reaction mixture to remove water has been used in both hydrogenation and decomposition processes (U.S. Pat. Nos. 5,550,301 and 3,927,108), but these methods do not remove the acidic by-products along with the water.
Organosilicon compounds have for some time been employed in the treatment of inorganic oxide surfaces such as inorganic oxide films, particulates and pigments, and fibers (such as glass fibers, aluminum fibers and steel fibers). The typical organosilicon treatment involves coating such surfaces with a hydrolyzate (and/or condensate of the hydrolyzate) of an organofunctional hydrolyzable silane. The treatment is typically supplied to the surface of the inorganic oxide whereby through the hydrolyzable groups or silanol groups (xe2x89xa1Sixe2x80x94OH), bonding through siloxy moieties (xe2x89xa1Sixe2x80x94Oxe2x80x94) is effected.
U.S. Pat. No. 2,722,504 modified the contact efficiency of catalysts and other materials by the incorporation of alkyl silanes onto the surface.
U.S. Pat. No. 4,451,572 describes a surface modified zeolite produced by reacting the zeolite with an organosilane.
WO 99/02264 describes but does not exemplify a supported ultrafine gold particle catalyst that has been rendered hydrophobic for the synthesis of hydrogen peroxide, one method of which is by treatment with silane.
U.S. Pat. No. 5,029,575 describes a method of removing the surface hydroxyl groups from a Rh/Al2O3 catalyst by silation.
Disclosed herein is an improved process for decomposing a hydroperoxide to form a decomposition reaction mixture containing a corresponding alcohol and ketone, the improvement comprising decomposing the hydroperoxide by contacting the hydroperoxide with a catalytic amount of a heterogeneous gold catalyst wherein the gold catalyst has been silanized with an organosilicon reagent. Further disclosed is the process wherein the heterogenous catalyst is supported on a catalyst support member.